Steven Karvellas, a former Director of the New York Mercantile Exchange, pleaded guilty to two felony counts of illegal trading in natural-gas markets. The charges result from an investigation by the Exchange, the CFTC, and the Manhattan District Attorney into "front-running," or the practice of waiting to execute a customer's order until the broker determines how the market is moving. WSJ, Ex-Nymex Official Pleads Guilty To 2 Counts in Gas-Trading Probe.